This invention relates to ferroelectric thin film processes, ferroelectric memory device structures and integrated processes for ferroelectric non-volatile memory devices, and specifically to a method of fabricating a ferroelectric thin film formed on a high-k gate oxide.
Metal, ferroelectrics, oxide, and silicon (MFOS) transistor ferroelectric memory devices have been proposed in the related applications. In order to provide a MFOS transistor memory device having desirable characteristics, the oxide must not react with nor diffuse into the ferroelectric and silicon substrate. On the other hand, ferroelectric thin films deposited on an oxide layer should have good ferroelectric properties for use in a memory transistor. Homogeneous ferroelectric thin films having desirable ferroelectric properties are difficult to deposit on gate oxides because of the interface mismatch between the high-k gate oxide and the ferroelectric materials. The mismatch results in random ferroelectric, such as PGO, thin films and coarser surface roughness. Seed layer processes have been developed for MFOS transistor ferroelectric memory applications to resolve the interface mismatch.
A method of forming a ferroelectric thin film on a high-k layer includes preparing a silicon substrate; forming a high-k layer on the substrate; depositing a seed layer of ferroelectric material at a relatively high temperature on the high-k layer; depositing a top layer of ferroelectric material on the seed layer at a relatively low temperature; and annealing the substrate, the high-k layer and the ferroelectric layers to form a ferroelectric thin film.
It is an object of the invention to provide a seed layer of FE material to enhance the FE deposition process.
A further object of the invention is to provide a FE device which is not degraded by an interface mismatch.
Another object of the invention is to provide a FE device using a seed layer processes to deposit homogeneous ferroelectric thin films on a high-k gate oxide, such as ZrO2, a HfO2 and (ZrxHf1-x)O2, in a MFOS transistor ferroelectric memory application.
Another object of the invention is to provide a MFOS one transistor device.
This summary and objectives of the invention are provided to enable quick comprehension of the nature of the invention. A more thorough understanding of the invention may be obtained by reference to the following detailed description of the preferred embodiment of the invention in connection with the drawings.